1. Field of the Invention
The present invention relates to a system for directly and selectively interconnecting, either mechanically, hydraulically, or pneumatically, two gas turbine engines for purposes of achieving both improved performance and economy of operation.
2. Description of the Prior Art
The relative simplicity, compactness, and light weight of the gas turbine engine cause it to be a preferred power plant for a variety of vehicles whether aircraft, watercraft, or landcraft. At the same time, gas turbines as previously used have been inherently inefficient when operated at less than their maximum power, and for many applications must so operate much of the time. Unfortunately, the thermal efficiency of gas turbines falls off very rapidly as the load is reduced, much more rapidly than in the case of conventional reciprocating internal combustion engines, and thus the specific fuel consumption rises proportionately. Indeed, in some instances, the high specific fuel consumption of the gas turbine engine under average operating conditions has outweighed the advantages of simplicity, compactness, and light weight, because the weight and volume of the extra fuel that had to be carried.
Various expedients have been attempted to raise the part power efficiency of gas turbines by changes in gas turbine engine designs including variable pitch blades in the compressor and turbine sections and by adding recuperators. However, such expedients have only partially improved the part power specific fuel consumption. One approach to solving the problem has been disclosed in U.S. Pat. No. 2,723,531 to Wosika et al. In that instance, efficiency was said to be greatly improved by employing in a power plant a plurality of small turbine units all adapted to be coupled to a single generator, and working only as many units as necessary to satisfy the power demand at anytime. For example, if two turbine units are employed, the specific fuel consumption can be reduced by almost one half, where the power plant must operate over a wide load range.
An early patent which relates to the use of multiple gas turbine engines of the turboprop type and to clutching arrangements between the engines and their associated propellers is disclosed in U.S. Pat. No. 2,838,913 to Peterson et al.
According to the invention disclosed in U.S. Pat. No. 3,416,309 to Elmes et al., an engine installation has at least two engines each of which is connected to drive at least one accessory mounted upon a respective gearbox through an output shaft. Power management control systems for multiple engine installations utilizing gas turbine engines are variously disclosed in U.S. Pat. Nos. 3,930,366 and 3,969,890 to Nelson, 3,963,372 to McLain et al. and to 4,137,721 to Glennon et al.
None of these patented systems, however, discloses an interconnection between the gas producers of the respective engines. It was in light of the state of the art as just mentioned that the present invention has been conceived and is now reduced to practice.